The present invention is directed to an apparatus for electrolytic surface treatment of bulk goods, particularly for the electro deposition of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte. The apparatus comprises a tank for the acceptance of the treatment bath, an arrangement for contacting the goods with one pole of an electrical source, at least one electrode arranged in the treatment bath and having the opposite polarity of the one pole and at least one vibrator conveyor comprising a heliacally ascending conveyor track for transporting of the goods through the treatment bath.
Aluminum deposited from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte is distinguished by its ductility, low number of pores, corrosion resistance and ability to be anodized. Since the access of air will effect a considerable diminution of the conductivity and the useful life of these electrolytes due to the reaction of the electrolytes with atmospheric oxygen and atmospheric humidity, the electro-plating must be undertaken in a treatment apparatus which operates under air exclusion or a protective atmosphere. In order for the access of air to be prevented during loading and unloading, these treatment apparatuses operating under an air exclusion utilize admission and discharge locks. These admission and discharge locks are fashioned as gas locks, as liquid locks, or as a combined gas-liquid lock and are equipped with conveyor means for conducting the goods to be treated through the locks.
U.S. Pat. No. 4,427,518, which is based on the same German application as European Patent No. 0,070,011, discloses an apparatus or facility for the electro deposition of metal, wherein bulk goods to be electro-plated are introduced into an electro-plating drum rotatably arranged in an electro-plating tank. The introduction of the goods is by an admissions station provided with conveying means. The goods are then conducted through the electro-plating drum, which is provided with a screw conveyor on an inside wall and then discharged at an exit station which is provided with a conveyor means. The electro-plating drum, which is provided with perforations, is, thereby, connected as a cathode, whereas the anode is arranged in the inside of the electro-plating drum. For the electro-deposition of aluminum from oxygen-free and water-free, aluminum-organic electrolyte, the electro-plating drum is constructed to be gas tight closeable and the space lying above the electrolyte level is charged with an inert gas. In addition, the admission and exit stations for the apparatus are additionally equipped with liquid locks.
In mass electro-plating, the bulk goods to be electro-plated must be held together during the galvanic processing so that every individual part is electrically contacted. On the other hand, the goods to be electro-plated should be spread out as far as possible so that the metal deposition can occur on as large as possible surface of the goods and an optimum uniform current density is guaranteed on all parts. Another essential precondition for achieving faultless metal coatings having a uniform layer thickness is an adequate mixing of the goods to be electro-plated during the galvanic processing. In what we refer to as a suspension-electro-plating device, this is achieved by transmitting an oscillating rotational motion onto the vessel filled with the goods to be electro-plated which vessel is immersed into the electrolyte (see the announcement in Galvanotechnik Vol. 75, 1984, No. 11, page 1399). The electrolyte exchange is also improved at the same time by means of an oscillatory motion of the vessel containing the goods. Given an apparatus or facility comprising an electro-plating drum, rotation of the drum suffices for the moving and mixing of the goods to be electro-plated. The individual parts are conveyed upward to a greater or lesser distance toward the top dependent on the form and wall friction of the drum and then roll or slide back down. An apparatus for mass electro-plating should also be equipped with conveyor means for transporting the goods to be electro-plated through the electrolyte with either a continuous or interval-wise admission and removel of the goods for electro-plating being enabled by the conveyor means in combination with corresponding admission and exit stations. Finally, both the motion of the goods, and the mixing as well as the transporting of the goods through the electrolyte should be undertaken so that a gentle treatment of the goods is guaranteed and sensitive parts are likewise not mechanically damaged during the galvanic processing.
An apparatus or device is disclosed in U.S. Pat. No. 3,649,490 for electrolytic surface treatment of bulk goods and this apparatus largely meets the demands recited above. In this known device, a vibratory conveyor having a helically ascending conveyor track is provided for the transport of the goods for electro-plating through the electrolyte, whereas either a cylinder surrounding the vibratory conveyor or rods which are perpendicularly suspending into the treatment bath serve as the electrode. Although a uniform spread of the goods on the conveyor track will occur due to the vibrations transmitted to the bulk goods, a uniform current density on all parts cannot be achieved during the electrolytic surface treatment.
The problems recited in the context of mass electro-plating also occur in the same way or at least in an analogous way in other processes for electrolytic treatment of bulk goods. Electrolytic pickling in acids or caustic solutions, electrolytic degreasing in alkaline baths and electrolytic polishing are examples of these other processes. Dependent on the type of electrolytic surface treatment, the bulk goods are connected either to a cathode or an anode. In electrolytical polishing, for example, the goods are connected to an anode.